CN1431073A - Method for preparing granules of nonoxidation stannic balls and forming machine used - Google Patents

Abstract

The invention discloses a method for preparing tin oxide-free particles and a used molding machine. The method is to continuously and evenly introduce molten metal liquid into a container with several uniform pores at the bottom under a protective atmosphere, let the container vibrate vertically, and make the molten tin liquid pass through the pores at the bottom with the inertial force generated by the vibration to form a Falling like raindrops; the falling metal droplets are pre-shrunk in a protective atmosphere, and then enter a reducing oil bath with a density > 1 to shrink into balls and cool to shape; the cooled solder balls are washed, dried, and packaged to obtain the product. The molding machine is composed of three parts: a melting furnace, a dropper and a spheroidizer. The dropper is designed to vibrate and disperse liquid drops, and the spheroidizer uses organic oil as a cooling molding medium. The product produced by the invention is spherical, has a bright surface, and has the characteristics of low cost, high efficiency and good quality.

Description

Preparation method of tin oxide-free particles and molding machine used

technical field

The invention relates to the manufacturing technology of low-melting-point metal particles, in particular to a method for preparing non-oxidized tin or tin alloy spherical particles and a molding machine used.

Background technique

Spherical metal particles are well known to have a wide variety of uses. At present, tin particles with an equivalent spherical diameter of 0.5-4.0 mm are generally produced by the metal liquid phase infusion method, specifically, the metal is melted and dropped into a cooling liquid through a drip tube or a drip tray to form it. In addition to the low production efficiency of the known method, what is more serious is that the sphericity of the tin particles produced is poor, and there are many particle conglomerates, which cannot avoid surface oxidation. Due to the large specific surface of the particles, the surface oxidation phenomenon directly reduces the product quality, resulting in many irreparable use defects, which seriously affects its use range. Such low-sphericity tin particles that cannot avoid surface oxidation are not suitable for precision electroplating, fine chemical products, electronic assembly, chemical reagents and additives.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art. On the one hand, it provides a method for preparing tin and tin alloy spherical particles with spherical particles, uniform particle size, bright surface, no oxidation, high efficiency and low cost; A molding machine used in the method is provided.

The preparation method of the tin oxide-free ball particles of the present invention is mainly completed by the following steps: metal melting, droplet dispersion, shrinkage molding and cooling, cleaning, drying and packaging. It is characterized by:

(1) Metal melting: the metal is melted under the protection of nitrogen or argon at a temperature of 250-350°C:

(2) Droplet dispersion: under the protection of nitrogen or argon, the molten tin liquid is evenly introduced into a container with several pores of the same diameter evenly distributed at the bottom. The number of pores is 10 to 10,000, and the aperture is Φ0.2 ～2.0mm, at a temperature of 300～400℃, apply a vertical vibration with an impact force of 1～100N to the container, so that the molten tin liquid will pass through the pores at the bottom with the inertial force generated by the vibration and fall in drop-shaped particles;

(3) Shrink molding and cooling: the falling metal droplets are pre-shrunk in nitrogen or argon, and then enter the reductive viscous oil with a temperature of 10-50°C and a density > 1 to shrink into balls and cooling molding;

(4) Cleaning, drying, and packaging: the shaped particles are first washed with tap water, then cleaned with ultrasonic waves for 5 to 30 minutes, and then dried for 10 to 60 minutes at a temperature of 100 to 140°C and a vacuum of 1 to 8Kpa. Finally, it is sealed and packaged under a vacuum condition of 1-8KPa.

The molding machine used in this method is composed of three parts: the melting furnace in the upper section, the dropper in the middle section, and the spheroidizing shaper in the lower section. It is characterized in that the dropper is designed to vibrate and disperse the dripping structure, and the top of the container is provided with a vibration device. The outside of the container is provided with an electric heating insulation layer, the side wall of the container is provided with a protective airflow inlet and outlet, and the bottom of the container is provided with a porous screen with several fine holes of the same diameter evenly distributed.

The upper part of the molding machine is provided with an electric heating insulation layer outside the melting furnace, the bottom is provided with a conduit connected to the dropper, the upper end of the conduit is provided with a flow-adjustable valve, and the furnace cover is provided with a protective airflow inlet and outlet.

The inner cavity of the spheroidizing molder in the lower section of the molding machine has mixed oil, and a refrigeration pipeline is arranged in the inner cavity, and the spheroidizing molder is equipped with an oil inlet and a protective airflow inlet and outlet, and a discharge valve with a control valve is installed at the bottom. mouth.

The melting furnace, dropper and spheroidizer are all circular, and their centers are on the same axis in the vertical direction.

The present invention is protected by nitrogen or argon to prevent the oxidation of liquid phase metal at high temperature; the droplet dispersion is carried out at a temperature of 300-400°C, which can ensure that the molten tin liquid has good fluidity and improve the resistance of the tin liquid to fine particles. The penetrating ability of the gap; when vertical vibration is applied to the droplet dispersion container, when the container returns to the high position from the low position within one vibration cycle, the fluid tin liquid will try to maintain the original inertia and spray out from the fine holes, and the uniform drop In this way, the droplet falls once every vibration, so that the droplet speed and particle size are in a controlled state; the falling metal droplet is pre-shrunk by its own surface tension in nitrogen or argon. , and then enter the viscous oil bath with a density > 1 at a temperature of 10-50°C. One is to continue to protect the droplets from oxidation, and the other is to reduce the settling velocity of the droplets in the oil so that the high-temperature metal droplets The heat exchange rate between the oil interface is reduced, thereby delaying the solidification of the droplet and ensuring that the metal droplet has sufficient shrinkage forming time; due to the high temperature at the phase interface where the oil and the metal droplet are in contact, the local high temperature activity can make the The metal droplet shrinks violently into a sphere; the oil used is reducing, which can ensure that the surface of the solder ball is bright without oxidation.

The present invention overcomes the deficiencies in the prior art and has the following advantages:

(1) Use controllable vibration to instill dispersed droplets to make the particle size of the product uniform, and pass through

 The particle size of the product can be adjusted by changing the process parameters.

(2) Inert reducing medium is used for full protection, the product is free from oxidation, the surface is bright, and the composition

Stablize.

(3) Oil is used as the spheroidizing agent, which is conducive to the shrinkage of metal droplets into balls, so that the product has an ideal ball

shape.

(4) The required equipment is simple, the structure is reasonable, the process is short, the efficiency is high, and the cost is low.

Description of drawings

Fig. 1 is the structural representation of the molding machine that the inventive method adopts.

Detailed ways

Referring to Fig. 1, the designed forming machine structure of the inventive method is as follows: the upper section is a melting furnace, the middle section is a drip disperser, and the lower section is a spheroidizing former. The melting furnace, droplet disperser and spheroidizer are all circular, and their centers are on the same axis in the vertical direction.

In the melting furnace part, a controllable electric heating wire 10 is provided on the side and bottom of the container shell 17, and an insulation layer 9 is provided on the outside of the electric heating wire 10, and a controllable valve 11 is provided on the bottom of the container shell 17 , A conduit 18 is connected below the valve 11, a furnace cover 12 is arranged on the top of the container shell 17, and air inlet and outlet holes 13, 14 and a thermometer 15 are arranged on the furnace cover.

The droplet disperser part is provided with a controllable electric heating wire 5 on the outside of the container shell 8, corresponding to the outside of the electric heating wire 5 is provided with an insulating layer 6, and the bottom of the container shell 8 is provided with a number of evenly distributed small needles. The perforated sieve 3 of the hole, the side wall of the container housing 8 is provided with inlet and outlet air holes 7, 20 and a thermometer 22, and the top of the container housing 8 is provided with an electromagnetic vibrator 19.

The part of the spheroidizer is filled with mixed organic oil 25 inside the container shell 26, the inner wall of the container shell 26 is provided with a controllable refrigeration pipe 1, and the upper end of the side wall of the container shell 26 is provided with an oil inlet 2 and The air inlet and outlet 4 and 23 and the thermometer 24, the bottom of the container housing 26 are provided with a material outlet 28 with a control valve 27. A circulation pipeline for mixing organic oil can also be set on the spheroidizer to facilitate continuous production.

Utilize above-mentioned forming machine, the preparation method of tin ball particle is carried out as follows:

(1) Metal melting: Put commercial tin ingots into the melting furnace, pass nitrogen gas, heat up and melt, and keep the temperature at 320±5°C.

(2) Droplet dispersion: under the protection of nitrogen, continuously and evenly introduce molten tin liquid into a dropper stainless steel container with a porous sieve at the bottom. The holes of the porous sieve are Φ0.3mm×100 holes. When the height of the tin liquid in the container reaches 50mm and the temperature is constant at 330±5°C, the vertical vibration with a frequency of 300 times per minute and an impact force of 2N is applied to the container through the vibration device, and the molten tin will flow from the bottom of the container at the same frequency. The fine pores rained down. At this time, immediately adjust the flow rate of the tin liquid flowing into the container to keep the height of the tin liquid in the container at 50±5mm.

(3) Shrink molding and cooling: The free-falling metal droplets are first pre-shrunk in the nitrogen on the upper part of the spheroidizer, and then fall into the mixed organic oil with the addition of reducing agent A at a constant temperature of 20±5 °C in the lower part Settled slowly. During the sinking process, the liquid droplets rapidly shrink into balls with the heat exchange at the phase interface and are cooled and formed. The formed tin or tin alloy balls are discharged from the discharge port at the bottom.

(4) Cleaning, drying, and packaging: The formed solder balls are first separated by a centrifuge and the liquid oil is recovered, then rinsed with tap water, and then placed in an ultrasonic cleaning machine for cleaning twice, each time for 5 minutes, and then heated at a temperature of 110°C. Dry for 30 minutes under the condition of vacuum degree of 2KPa, after cooling, seal and pack under the condition of vacuum condition of 2KPa, and obtain bright and non-oxidized solder ball products with a particle size of Φ1.0±0.05mm.

The above is one of the preferred embodiments of the present invention.

The raw materials used in another embodiment of the present invention are 63% Sn and 37% Pb alloy; the aperture of the porous sieve is Φ0.3mm; the vibration frequency is 450 times/min, and the vibration force is 3N; other parameters are the same as the previous embodiment. The obtained product is bright tin-lead alloy spherical particles of Φ1.0±0.05mm.

The method of the present invention can also enumerate several embodiments. Specifically, it is only necessary to change the relevant parameters such as the aperture, vibration force and temperature of the container used for droplet dispersion to obtain bright solder ball products with different particle sizes.

The idea of the method of the present invention can be generalized and applied to the manufacture of other low-melting metal spherical particles.

Claims (10)

1. A method for preparing tin oxide-free particles is characterized in that it is carried out in the following steps: metal melting, droplet dispersion, shrinkage molding and cooling, cleaning, drying, packaging; said droplet dispersion is carried out under nitrogen or Under the protection of argon, the molten tin or tin alloy liquid is continuously introduced into the container with a number of porous screens with uniformly distributed pores of the same diameter at the bottom, and the container is vibrated vertically so that the molten tin or tin alloy liquid passes through the container with the inertial force generated by the vibration. Raindrops fall through the pores in the bottom of the container. 2. The preparation method according to claim 1, characterized in that: the shrinkage molding and cooling are to make the free-falling metal droplets pre-shrink in nitrogen or argon, and then enter into a The viscous mixed oil is shrunk into a ball and cooled to shape. 3. The preparation method according to claim 1 or 2, characterized in that the metal melting, droplet dispersion, shrinkage molding and cooling are carried out under the protection of nitrogen or argon. 4. The preparation method according to claim 1 or 2, characterized in that the droplet dispersion temperature is 300-400°C, the vibration frequency applied to the container is 100-1000 times per minute, and the impact force is 1-100N. 5. The preparation method according to claim 1 or 2, characterized in that the temperature of the mixed oil used for shrink molding and cooling is 10-50°C. 6. The preparation method according to claim 1 or 2, characterized in that the melting temperature of the melting furnace is 250-350°C, the number of holes in the porous sieve is 10-10,000, and the hole diameter is Φ0.2-2.0 mm. 7. The preparation method according to claim 1 or 2, characterized in that: the cleaning, drying, and packaging are performed by washing the cooled tin ball particles with tap water and ultrasonic cleaning, and then vacuum drying at 100-140°C. Finally the package is sealed under vacuum. 8. A molding machine for preparing non-oxide tin ball particles, which consists of three parts: the melting furnace in the upper section, the dropper in the middle section, and the spheroidizing molder in the lower section. It is characterized in that the dropper is designed to vibrate and disperse the dripping liquid Structure, the upper part is provided with a vibration device, the outer part of the middle container is provided with an electric heating insulation layer, the side wall is provided with a protective airflow inlet and outlet, and the bottom of the dropper is provided with a porous screen with several fine holes of the same diameter evenly distributed. 9. The forming machine according to claim 8, characterized in that the inner chamber of the lower segment of the spheroidizing former has mixed oil, the inner chamber is provided with a cooling pipeline, and the spheroidizing former is provided with an oil inlet and a protective airflow inlet and outlet , the bottom is provided with a discharge port with a control valve. 10. The forming machine according to claim 8 or 9, characterized in that a heating insulation layer is provided outside the melting furnace in the upper section, a conduit is provided at the bottom to communicate with the dropper, a bottom valve that can adjust the flow rate is provided on the conduit, and a bottom valve is provided on the furnace cover. There is a protective airflow inlet and outlet.